The invention relates to recovering a gaseous product gas containing hydrocarbon values from a hydrocarbon-containing formation, and more particularly the present invention relates to injecting a mixture of oxidizing gas and steam into a lateral conduit in a partially depleted petroleum-containing formation to produce a combustible product gas, analyzing the produced product gas for values of selected gaseous components and, based on such values, controlling the reactions between the mixture of oxidizing gas and steam and the petroleum in the formation to optimize production of product gas in the formation, and recovering the product gas through a recovery well.
A major problem has been the economic recovery of hydrocarbons from reservoirs that cannot be produced economically by conventional techniques. This problem is particularly acute when it is desired to recover hydrocarbons from partially depleted heavy-oil reservoirs. Although the term "heavy oil" is only relative nomenclature and may be defined differently in different localities, it usually refers to oils with a gravity of less than 20.degree. API.
Heretofore, many processes have been utilized in attempting to recover hydrocarbon values from such reservoirs. The application of heat to the oil by steam injection or underground combustion has been done to assist recovery. Various underground gasification processes have been suggested, particularly for use in tar sands as taught in U.S. Pat. No. 3,250,327. There is still a need, however, for a process which will economically maximize recovery of hydrocarbon values from partially depleted heavy-oil reservoirs.